Solenoid driving means

ABSTRACT

Apparatus for sequentially energizing and maintaining a pulrality of solenoids in operated condition for a predetermined period of time includes electro-optical distributive means for sequentially applying triggering pulses circuits, a plurality of solenoid operating amplifiers, each of said circuits including two operational amplifiers, one of which is included in a circuit for providing a solenoid energizing pulse, and the other of which is included in a circuit for providing a solenoid holding pulse.

United States Patent 1 1 Myers 5] June 10, 1975 [52] US. Cl...... 317/1485 R; 123/32 EA; 317/124;

317/139 [51] Int. Cl. H01h 47/32 [58] Field of Search 317/124, 127, 137, 139,

317/140, 148.5 R, DIG. 4, DIG. 6; 250/206, 208, 233, 578, 236; 123/32 EA; 307/270, 293

7/1972 Dyer 317/1485 R 2/1974 Canup et al. 250/233 Primary Examiner.l. D. Miller Assistant Examiner-I-larry E. Moose, Jr. Attorney, Agent, or FirmDybvig & Dybvig 1571 ABSTRACT Apparatus for sequentially energizing and maintaining a pulrality of solenoids in operated condition for apredetermined period of time includes electro-optical distributive means for sequentially applying triggering pulses circuits, a plurality of solenoid operating amplifiers, each of said circuits including two operational amplifiers, one of which is included in a circuit for [56] References Clted providing a solenoid energizing pulse, and the other of UNITED STATES PATENTS which is included in a circuit for providing a solenoid 3,340,407 9/1967 Sinclair 6 pulse. 3,386,000 5/1968 Farr 317/124 3,530,341 9/ 1970 Hutchinson 317/137 9 Claims, 6 Drawing Figures 8"- I4 I I A l l 1.1! I 34 2 1- 1 I rr-" [iffI-Il/ I/ 38 v 1 I I I 22, 32 I1 PATENTEDJUH 10 I915 I 3,889,162.

HIGH VOLTAGE PULSE I I Low VOLTAGE HOLDING FAST RISE DUE To Hleri VOLTAGE HOLDING CURRENT SOLENOID DRIVING MEANS BACKGROUND OF THE INVENTION The invention solves the problem of providing a solenoid operating circuit which serves as an interface between low power level input triggering means, such as light-emitting diodes, and high-speed outputs for fast solenoid operation, which require high voltage levels.

SUMMARY OF THE INVENTION The present invention resides in a solenoid drive circuit and in triggering means for applying an input signal to said circuit at periodic intervals. The solenoid drive circuit includes a first operational amplifier responsive to the input signal from the triggering means, a second operational amplifier having an inverting input connected to the output of the first operational amplifier, timing means interposed in the circuit path from the output of the first operational amplifier to the inverting input of the second operational amplifier for controlling the duration of the signal applied to the second operational amplifier, reset means for resetting the timing means, a low voltage power driver connected to the output of the first operational amplifier, and a high voltage power driver connected to the output of the second operational amplifier. This solenoid drive circuit provides an initial high-voltage energizing pulse to a solenoid connected to said circuit, followed by a lowvoltage holding pulse to maintain said solenoid in energized condition for the duration of said low voltage pulse. The triggering means employed to provide an input pulse to the solenoid drive circuit may be of the electro-optical type, capable of applying periodic sequential input pulses to a plurality of solenoid energizing circuits by use of a plurality of radiation-emitting and radiation-sensitive elements arranged in confronting sets or pairs, with a blocking element or radiation shutter arranged between the radiation-emitting and radiation-sensitive elements, and partaking of periodic movements so as to periodically and sequentially block the radiation paths between sets of said radiationemitting and radiation-sensitive.elements. An opaque mask is utilized to prohibit interaction between sets of elements and increase angular accuracy.

The solenoid control system of the present invention may be used for control of solenoid operated fuel injection systems in diesel engines, but is not limited to such, and is also useful in other applications where highspeed solenoid operation is required.

It is accordingly an object of the present invention to provide an improved solenoid control system.

A further object is to provide a solenoid control system employing electro-optical means for sequentially triggering a plurality of solenoid operating circuits.

An additional object is to provide a solenoid operating circuit capable of producing a solenoid energizing pulse having an initial high-voltage energizing portion followed by a lower voltage holding portion.

Further objects and features of the invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings illustrating the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an electro-optical sequential switching mechanism which may be employed in the present invention.

FIG. 2 is a sectional view of the electro-optical sequential switching mechanism taken on line 22 of FIG. 1.

FIG. 3 is a schematic diagram of the solenoid operating circuitry of the present invention.

FIG. 4 is a plan view of the mask means of the electro-optical switching mechanism.

FIGS. 4A and 4B are waveform diagrams of voltages and currents applied to energize and hold a solenoid in energized condition in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2 of the drawing, there is shown an electro-optical sequentially distributive switching or triggering mechanism 10, including a base 12, a cap 14 and a double cylindrical wall 16, 17 to the outer wall of which the cap is secured by a fastener 18. These elements are sealed to prevent ambient light from entering the interior of the mechanism 10. Bearings 20 and 22 in the cap and base, respectively, support a shaft 24 for rotatiopal movement within the mechanism 10. The shaft 24 may be driven continuously by any suitable means. In the application of the present invention to a solenoid energizing means for a fuel injection system of a diesel engine, the shaft. 24 may be driven by means of suitable gearing from'the crankshaft of the engine, on which the base 12 of the mechanism 10 is mounted by any suitable means 23, O ring seals 25 being utilized to prevent fluid leakage.

Secured to the shaft 24 for rotation therewith is a shutter 26, approximately one-half of the circumference of which is a reduced radius portion 28. A cut-out 29 in the remaining portion of the shutter 26 provides compensation in mass for the reduced radius portion 28, to prevent imbalance during rotation of the shutter 26.

Spaced above and below the shutter 26 and parallel to its plane of rotation are first and second support elements 30 and 32, which are supported by the inner wall 17, and which include projections 34 and 36, respectively, extending outside the mechanism 10 for electrical connection purposes.

Positioned on the element 30, spaced equidistant along a circular path having as its center the center of rotation of the shaft 24, are a plurality, shown as six in the illustrated embodiment, of radiation-emitting devices 40 of any suitable type. In the illustrated embodiment of the invention, these are light emitting diodes of type MLED 900, manufactured by Motorola, Incorporated.

Positioned on the element 32, each in the same relative position as the radiation-emitting devices 40, in registry therewith, are a plurality of radiation-sensing devices 38, of any suitable type having radiation matching characteristics compatible with said radiationemitting devices. In the illustrated embodiment, these are radiation detectors of type MRD 450, manufactured by Motorola, Incorporated.

interposed between the radiation emitters and detectors and below the shutter 26 closer to the detectors 38 is a fixed shielding means or mask 41 having radially elongated perforations 43, as shown in FIG. 4, which restrict light passage to a narrow beam. The mask 41 is sufficiently thick in relation to the side-to-side widths of'the perforations 43 and its separation from the emitter devices 40 to prevent cross-coupling between pairs of emitter and detector devices. Sharp edged shadowing of emitter light by the mask also enhances the sharpness or accuracy with which circuits to be described are triggered by operation of the emitter and detector devices.

Operation of the mechanism is as follows. The utilizing device, such as a diesel engine, with which the mechanism 10 is associated, causes the shaft 24 and the shutter 26 affixed thereto, to rotate continuously. Examination of FIG. 2 will reveal that as the shutter 26 rotates, the paths between associated pairs of radiationemitting devices 40 and radiation-sensitive devices 38 are successively opened and closed to provide pulses which may be used to trigger the operation of associated circuitry. In the illustrated embodiment, paths are normally open for three of said pairs at any given time.

The circuitry in which the devices 38 and 40 are utilized is shown in FIG. 3, and will now be described.

The radiation-emitting devices 40 are serially connected in a circuit path which extends from a source 42 of operating potential. over the serially-connected radiatiomemitting devices 40, a regulating means, shown in FIG. 3 as an NPN transistor 44, and through a resistor 45 to a reference potential, shown as ground. A parallel path extends from the source 42 over a resistor 46 to the base of the transistor 44, and thence to ground over a zener diode 47. The circuit can be recognized as a constant current regulator with a current which is determined by the difference between the zener voltage and the base-emitter voltage of the transistor 44 impressed across the resistor 45, i.e. I==('V -V- be)/ Only one of the circuits associated with the radiationsensitive devices 38 is shown in detail in FIG. 3, with the remainder of such circuits being represented by blocks, since all are identical. It will be noted that the shutter 26 and the radiation paths are represented schematically in FIG. 3. While representative voltages and certain other circuit values are given in the ensuing description, it will be recognized that these are only included for purposes of illustration, and that the proper functioning of the circuitry is not dependent upon the use of these specific values.

In the circuit of FIG. 3, the emitter of the radiationsensitive device 38 is connected to a reference potential shown as ground, and its collector is connected through a resistor 44 to a source 84 of +28 volts potential. The collector of the device 38 is also connected over a resistor 46 to the non-inverting input of an operation amplifier 48. The inverting input of the operational amplifier 48 is connected to a source of +1 4 volts potential to provide a threshold value for said amplifier.

From the output of the operational amplifier 48, a first circuit branch provides a feedback path extending over a resistor 50 to the non-inverting input of said amplifier. A second circuit branch extends over a diode 52 and a resistor 54 to the base of a PNP transistor 56. A circuit path connects the base of said transistor through a resistor 57 to its emitter, which is also connected to a source 59 of +6 volts solenoid holding supply potential. The collector of the transistor 56 is directly connected to the base of an NPN transistor 58, the collector of which is connected to the same source of potential as the emitter of transistor 56. The emitter and base of the transistor 58 are connected together through a resistor 60, and said emitter is further connected over a diode 62 to a circuit node 64. From the node 64 a circuit path extends to a circuit node 66 and from thence to one side of a solenoid 68 which will typically be of approximately 2 ohms impedance. The other side of the solenoid 68 is grounded at circuit node 69. From the node 66 there also extends a circuit path over a diode 70 and through a zener diode 112 to the grounded circuit node 69. The diode 70 and zener diode 112 provide a discharge path for the solenoid 68 when the latter is de-energized. The corresponding solenoids for the remaining energizing circuits, not shown in detail, are also connected each over a diode and through the same zener diode 112 to the grounded node 69.

Referring again to the operational amplifier 48, a third circuit branch extends from the output of said amplifier over a capacitor 74 to a circuit node 76. A first branch from the node 76 extends to the inverting input of a second operational amplifier 78, and a second branch extends through a resistor 80 and a potentiometer 82 to the source 84 of +28 volts potential. A diode 86 is connected between the source 84 and the inverting input of the operational amplifier 78. The noninverting input of the amplifier 78 is connected through a resistor 88 to a +14 volt source of potential to provide a threshold value for said amplifier, and through a resistor 90 to the output of said amplifier to provide a feedback path.

The output of the amplifier 78 is also connected through a zener diode 92 and a resistor 94 to the base of an NPN transistor 96. The base of said transistor is also connected to ground through a resistor 97 and the emitter of said transistor is also connected to ground.

The collector of the transistor 96 is connected through a resistor 98 to the base of a PNP transistor 100, which base is also connected through resistor 102 to a source 104 of +88 volts solenoid energizing supply potential. The emitter of the transistor is directly connected to the source 104, as is the collector of an NPN transistor 106, the base of which is directly connected to the collector of the transistor 100 through a circuit node 108. From the node 108 a path extends through a resistor 110 to the previously mentioned node 64, which is also directly connected to the emitter of the transistor 106.

Referring once more to the operational amlifiers 48 and 78, these may consist of a dual operational amplifier, such as a dual 741, manufactured by Texas Instruments, Inc., with biasing circuits as shown in FIG. 3.

Operation of the circuit of FIG. 3 will now be described. When radiation from a radiation-emitting device 40 is permitted by the shutter 26 to fall upon the associated radiation-sensitive device 38, said device is rendered conducting, causing the voltage level at the non-inverting input of the operational amplifier 48 to drop sharply, which results in a corresponding drop in the level of the output of said amplifier, with the path including resistor 50 providing positive feedback to insure fast switching, regardless of how slowly the signal input is changing. Thus the output of the amplifier 48 is always shifted sharply to either a low-voltage state of about 2 volts DC or a high-voltage state of about 26 volts DC. I

A low voltage signal level at the output of the amplifier 48 results in two occurrences. First, the low-voltage driving circuit comprising 'the transistors 56 and 58 and associated circuit components is turned on. Current flows from the potential source 59 through the emitterbase junction of the transistor 56, through the resistor 54 and the diode 52 into the output of the amplifier 48. The transistor 56 is thus rendered conducting, and its collector supplies current to the base of the transistor 58, biasing said transistor to a conductive state, so that following a short-duration high voltage energizing pulse applied to the solenoid 68, as will subsequently be described, current is supplied from the source 59 through the diode 62 and the circuit nodes 64 and 66 to the solenoid coil 68, the circuit being completed to ground at circuit node 69. The resistors 57 and 60 bypass junction leakage currents to provide high resistance, in the off states of the respective transistors 56 and 58. l

A low-voltage-level signal at the output of the amplifier 48 also causes a high-voltage short-duration solenoid energizing pulse to be provided by a high-voltage driving circuit comprising the transistors 96, 100 and 106 and associated circuit components in the following manner. The inverting terminal of the operational amplifier 78 is driven to a low level by the output of the operational amplifier 48 which is coupled over the capacitor 74 to said input. This causes the output of the amplifier 78 to be triggered to a high voltage level of about 26 volts DC, supplying current through the zener diode 92 and the resistor 94 to the base of the transistor 96, rendering it conductive so that current is supplied through the resistor 98 to the base of the transistor 100, causing it, in turn, to conduct, so that current is supplied to the base of the transistor 106. This transistor now commences conducting, supplying current therethrough to the solenoid 68, completing a circuit through the circuit node 66 and the solenoid 68 to ground at circuit node 69. Since the output voltage is now in excess of 80 volts DC, the diode 62 is necessary to protect the transistors 58 and 56 from excessive reverse voltage. The resistors 97, 102 and 110 bypass junction leakage currents to provide high resistance in the off-states of the transistors 96, 100 and 106, while the zener diode 92 blocks the off-state voltage of the amplifier 78, typically 2 volts DC.

The transistor 58 is biased to a conducting condition, but does not actually conduct during the high voltage pulse applied to the solenoid 68. Not until the highvoltage pulse terminates does the transistor 58 supply current through the diode 62 to the solenoid 68.

Wave forms representing the voltage and current during the energization and holding pulses applied to the solenoid 68 are shown in FIG. 4A and 4B, respectively, of the drawing. It will be noted from these Figures that a relatively shortduration high-voltage pulse of approximately 3 to 5 milliseconds is followed by a somewhat longer holding pulse. Application of the 88- volt pulse to the two-ohm solenoid results in a steadystate power level of approximately 4 kilowatts. It is thus important that this high-voltage energizing pulse be of short duration in order to prevent solenoid overheating. It will also be noted from FIG. 4A that deenergization of the solenoid 68 at termination of the holding pulse results in a back E.M.F. of a magnitude limited by the clamping voltage of the zener diode l 12.

Timed duration of the high-voltage pulse is obtained in the following manner. When the output of the amplifier 48 shifts to a low voltage level, the circuit node 76 also shifts to a low level. The capacitor 74 then begins to charge through the circuit branch including the resistor and the potentiometer 82, with a time constant determined by the resistance of the resistor 80 and the potentiometer 82, and the capacitance of the capacitor 74, as is well known. When the voltage level at the output of the amplifier 48 plus the capacitor voltage reaches a threshold value equal to that set on the non-inverting input of the amplifier 78 by the circuit path including the resistors 88 and 90, the output of the amplifier 78'is shifted regeneratively to a low voltage level, due to the positive feedback supplied by the path including the resistor 90. This shift of the amplifier output to the low voltage level terminates the high-voltage solenoid energizingpulse. it will be seen that the duration of this pulse may be varied by changing the setting of the potentiometer 82, which alters the time constant of the RC network comprising capacitor 74, resistor 80 and potentiometer 82.

The diode 86 is not a factor in timing of the duration of the high-voltage solenoid energizing pulse. However, it provides a fast reset of the voltage of the capacitor 74 when the output of the amplifier 48 is again shifted to a high level.

Although this invention has been described in its preferred form, with a certain degree of particularity, it is to be understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

Having thus described my invention, I claim:

1. A solenoid driving circuit comprising, in combination,

first operational amplifier means having an inverting input, a non-inverting input, an output, and feedback means connecting the output and the noninverting input;

input signal means connected to the non-inverting input of said first operational amplifier means and capable of applying an input signal thereto; means for connecting a source of threshold potential to the inverting input of said first operational amplifier means; second operational amplifier means having an inverting input, a non-inverting input, ,an output, and feedback means connecting the {output and the non-inverting input; means for connecting a source of tlireshold potential to the non-inverting input of said second operational amplifier means; I signal transmitting means for applying a signal from the output of said first operational amplifier means to the inverting input of said second operational amplifier means, and including signal duration limiting means;

high-voltage driver means connected to the output of said second operational amplifier means and responsive to a signal on said output to produce a high-voltage solenoid-energizing pulse; and low-voltage driver means connected to the output of said first operational amplifier means and responsive to a signal on said output to produce a .lowvoltage solenoid holding pulse following termination of the high voltage solenoid-energizing pulse.

2. The solenoid driving circuit of claim 1 in which the signal duration limiting means includes capacitive and resistive elements.

3. The solenoid driving circuit of claim 1, also including fast reset means connected to the inverting input of said second operational amplifier means for enabling the rapid resetting of the signal duration limiting means.

4. The solenoid driving circuit of claim 3 in which the fast reset means includes unidirectional signal translating means.

5. The solenoid driving circuit of claim 1 in which the high-voltage solenoid energizing pulse is of shorter duration than the low-voltage solenoid holding pulse.

input of said first operational amplifier means and capable of applying an input signal thereto;

means for connecting a source of threshold potential to the inverting input of said first operational amplifier means;

second operational amplifier means having an invert-.

ing input, a non-inverting input, an output, and feedback means connecting the output and the non-inverting input;

means for connecting a source of threshold potential to the non-inverting input of said second operational amplifier means;

signal transmitting means for applying a signal from the output of said first operational amplifier means to the inverting input of said second operational amplifier means, and including signal duration limiting means; and

high-voltage driver means connected to the output of said second operational amplifier means and responsive to a signal on said output to produce a high-voltage solenoid-energizing pulse.

7. The solenoid driving circuit of claim 6 in which the signal duration limiting means includes capacitive and resistive elements.

8. Thesolenoid driving circuit of claim 6, also including fast reset means connected to the inverting input of said second operational amplifier means for enabling the rapid resetting of the signal duration limiting means.

9. The solenoid driving circuit of claim 8 in which the fast reset means includes unidirectional signal translating means.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. I I 3! DATED 1 June 10, 1975 it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[57] ABSTRACT, line 2, change "pularlity" to pulraiity line 5, after pulses, delete "circuits" and insert to before "a"; lines 5 and 6, delete "amplifiers" and insert circuits Signed and Scaled this A ttes t:

RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmissr'mwr ufParenrs and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3,889,162

DATED June 10, 1975 It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below;

[57] ABSTRACT, line 2, change "pularlity" to P Y line 5, after pulses, delete "circuits" and insert to before "a"; lines 5 and 6, delete "amplifiers" and insert circuits Signed and Sealed this twenty-fourth D a y Of February 19 76 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN AIHSII'ng Offic Commissioner ufParenls and Trademarks 

1. A solenoid driving circuit comprising, in combination, first operational amplifier means having an inverting input, a non-inverting input, an output, and feedback means connecting the output and the non-inverting input; input signal means connected to the non-inverting input of said first operational amplifier means and capable of applying an input signal thereto; means for connecting a source of threshold potential to the inverting input of said first operational amplifier means; second operational amplifier means having an inverting input, a non-inverting input, an output, and feedback means connecting the output and the non-inverting input; means for connecting a source of threshold potential to the noninverting input of said second operational amplifier means; signal transmitting means for applying a signal from the output of said first operational amplifier means to the inverting input of said second operational amplifier means, and including signal duration limiting means; high-voltage driver means connected to the output of said second operational amplifier means and responsive to a signal on said output to produce a high-voltage solenoid-energizing pulse; and low-voltage driver means connected to the output of said first operational amplifier means and responsive to a signal on said output to produce a low-voltage solenoid holding pulse following termination of the high voltage solenoid-energizing pulse.
 2. The solenoid driving circuit of claim 1 in which the signal duration limiting means includes capacitive and resistive elements.
 3. The solenoid driving circuit of claim 1, also including fast reset means connected to the inverting input of said second operational amplifier means for enabling the rapid resetting of the signal duration limiting means.
 4. The solenoid driving circuit of claim 3 in which the fast reset means includes unidirectional signal translating means.
 5. The solenoid driving circuit of claim 1 in which the high-voltage solenoid energizing pulse is of shorter duration than the low-voltage solenoid holding pulse.
 6. A solenoid driving circuit comprising, in combination, first operational amplifier means having an inverting input, a non-inverting input, an output, and feedback means connecting the output and the non-inverting input; input signal means connected to the non-inverting input of said first operational amplifier means and capable of applying an input signal thereto; means for connecting a source of threshold potential to the inverting input of said first operational amplifier means; second operational amplifier means having an inverting input, a non-inverting input, an output, and feedback means connecting the output and the non-inverting input; means for connecting a source of threshold potential to the non-inverting input of said second operational amplifier means; signal transmitting means for applying a signal from the output of said first operational amplifier means to the inverting input of said second operational amplifier means, and including signal duration limiting means; and high-voltage driver means connected to the output of said second operational amplifier means and responsive to a signal on said output to produce a high-voltage solenoid-energizing pulse.
 7. The solenoid driving circuit of claim 6 in which the signal duration limiting means includes capacitive and resistive elements.
 8. The solenoid driving circuit of claim 6, also including fast reset means connected to the inverting input of said second operational amplifier means for enabling the rapid resetting of the signal duration limiting means.
 9. The solenoid driving circuit of claim 8 in which the fast reset means includes unidirectional signal translating means. 